Effect of Nanoconfinement on NMR Relaxation of Heptane in Kerogen from Molecular Simulations and Measurements.

J Phys Chem Lett

Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main Street, Houston, Texas77005, United States.

Published: February 2023

Kerogen-rich shale reservoirs will play a key role during the energy transition, yet the effects of nanoconfinement on the NMR relaxation of hydrocarbons in kerogen are poorly understood. We use atomistic MD simulations to investigate the effects of nanoconfinement on the H NMR relaxation times and of heptane in kerogen. In the case of , we discover the important role of confinement in reducing by ∼3 orders of magnitude from that of bulk heptane, in agreement with measurements of heptane dissolved in kerogen from the Kimmeridge Shale, without any models or free parameters. In the case of , we discover that confinement breaks spatial isotropy and gives rise to residual dipolar coupling which reduces by ∼5 orders of magnitude from the value for bulk heptane. We use the simulated to calibrate the surface relaxivity and thence predict the pore-size distribution of the organic nanopores in kerogen, without additional experimental data.

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http://dx.doi.org/10.1021/acs.jpclett.2c03699DOI Listing

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